im not that expert to tell you what anti virus program to use. it also depends on your pc,
but AVG 8.0 is a lot better compare to avast 4.8, avast did not pass the VB100% with this product. As for AVG 8.0 it did pass VB100% for all operating systems detected, ICSA Labs, WestCoast Lab Checkmark Level 1, Level 2 and Trojan certifications, recommended by CNET and PC pro. Avast 4.8 has a lot of false positive because the software like kaspersky is very intrusive. Also in AV comparatives last February AVG 8.0 scored higher than Avast.
Avast is still a great anti virus, but for me after several testings, i chose AVG 8.0, actually i tested 4 different anti virus software that is free on the market today. includes AVG 8.0 Free, Avast 4.8 home Edition Free, PC Tools 4.0 Free Anti Virus and Avira AntiVir Personal Free Edition.
here is what i experience on different testing of the products.
Avast 4.8 - Its Very intrusive but high detection rate, i installed it in one of the pc in the office, Avast 4.8 destroyed the database of our Accounting & Inventory Management System, by way of scanning every details that goes in and out of the system. which causes write delay on the database of our system. but if you use avast at home with no other network aside from the internet, it has a good protection, lighter that AVG on system resources. its only problem is very intrusive which causes false positive.
Avira AntiVir - High detection rates, highest actually according to lates AV comparatives, it did pass VB100% this year. but doesnt have anti spyware included in the scanning engine. upates are in big bytes and very slow. sometimes its hard to update. but for me vey good in protecting your pc. No email scanner by the way.
PC Tools - Fast updates, fast scanning, this is very light on system resources at around 4-10mb intelli guard (real time monitor). but dont have anti spyware included, no anti rootkit, and no certification on certain testing like VB100%, ICSA, WestCoast Lab and i dont see PC tool in the AV comparatives latest reviews. So it up to you to test this products. but i used this anti virus in one pc in the office, its been running for 1 month, and up to now no virus infected that pc. but you need to team this with anti spyware program like spybot S&D or windows defender.
AVG - best of all for me, fast updates, nice forums. and support from AVG but Avast has the best support to its user even if your using free edition. Nice interface, for me the best GUI, high detection rates with no false positve, certified by all major certification.
Cons of AVG - no anti rootkit for free edition, and it not light on system resources, it uses 50+mb (for resident shield "real time monitor) so if you want to use AVG you should have at lest 512mb of ram or higher. avast real time monitor only uses 16-28mb, PC Tools 4-10mb, Avira 10-18mb.
i hope you read my notes here. it can help you select which anti virus to use.